A population based investigation of head injuries and symptoms of concussion of children and adolescents in schools.

OBJECTIVE: To examine the incidence of head injury and symptoms of concussion among children at school and to determine the relationship of age, gender, and cause to incidence rates. DESIGN: Incident reports involving head injury for schools in the Province of Ontario, Canada during the year 2000 were evaluated. PARTICIPANTS: The population base for the schools represented was 1 372 979 children aged 6 to 16. SETTING: 95% of schools in the province of Ontario, Canada participated in the injury reporting system. MAIN OUTCOME MEASURES: A head injury was defined as any injury to the head that came to the attention of a school official. Head injuries accompanied by symptoms of concussion became a secondary outcome measure. RESULTS: There were 11 068 unduplicated head injury reports for the year 2000 of which 1861 qualified as producing signs or symptoms of concussion. Young children were more likely to have a head injury than older children, but slightly less likely to experience concussive symptoms. The primary cause of injury to young children was falls. Older children were more likely to receive head injuries and symptoms of concussion from sports activities. CONCLUSIONS: Overall rate of injury (3.98 per 100 children) was consistent with previous studies using prospective injury reporting systems. Probability of a head injury with symptoms of concussion among schoolchildren was only 1.9% for boys and <1% for girls during the course of their school years. There is ample justification for prevention efforts in schools.

Effects of water immersion on pulmonary function in asthmatics.

Immersion induces air trapping in the lungs, as does asthma. Consequently, when using diving apparatus, asthmatics may face greater risk than non-asthmatics of pulmonary barotrauma (PBT) during ascent. We studied the pulmonary airflows and closing capacities (CC = closing volume + residual volume) in subjects with exercise-induced asthma (A, n = 12) and in healthy controls (C, n = 11) under four conditions: dry and immersed, both before and after exercise (treadmill running, non-immersed). Immersed, both C and A had significant and equivalent reductions in vital capacity, FEV1, FEV1/FVC, and FEF25%-75%. Post-exercise and immersed, pulmonary airflows deteriorated further in A but were better in C: FEV1 (A, 3.6 +/- 0.8 liter vs. 3.3 +/- 0.8 liter, P = 0.001; C, 3.9 +/- 0.5 liter vs. 4.1 +/- 0.6 liter, P = 0.006), FEF25-75% (A, 3.5 +/- 1.0 liter x s(-1) vs. 3.0 +/- 0.8 liter x s(-1). P < 0.05; C, 4.0 +/- 0.9 liter x s(-1) vs. 4.3 +/- 0.9 liter x s(-1), P < 0.05). Therefore, in contrast to C, A subjects had reduced pulmonary airflows during immersion after exercise. Furthermore, A subjects more often had no closing volume phase IV when immersed after exercise than C (P = 0.005). Interpreting the absence of phase IV as indicative of more air trapping in the asthmatics during immersion after exercise would be consistent with the reductions in airflow.

Myasthenia gravis in a collegiate football player.

A 17-yr-old Division I-AA collegiate offensive lineman developed unilateral ptosis shortly after minor head trauma during a scrimmage. The subsequent temporal profile of the ptosis, a history of a similar event lasting a short period of time 2 yr earlier, and the results of his clinical and electrophysiologic examinations established a diagnosis of very mild, generalized, antibody-negative myasthenia gravis (MG). His desire to continue playing football posed several additional management problems for which there was no published guidance. We started him on alternate-day, high-dose prednisone therapy with potassium and calcium supplementation, and allowed him to partake in conditioning but no contact. Except for residual decreased exercise tolerance, he improved symptomatically and experienced no serious adverse effects from the illness or the treatment during his first season, despite imperfect drug compliance. His MG eventually came under excellent symptomatic control, allowing initiation of a slow taper of the prednisone before his second season. Shortly thereafter, he abruptly stopped the prednisone without seeking medical advice. He continued to experience mild left ptosis and a mild decrease in intense exercise tolerance. He decided to forego his senior season of collegiate football after a bout of severe mechanical low-back pain incurred during spring football practice and limited his athletic activity thereafter to recreational sports.

Closed flexor tendon disruption in athletes.

Closed tendon injuries of the hand and wrist are very common in the athletic population. Most of these injuries, especially those involving the extensor tendons, can be treated successfully with nonoperative management if seen acutely. Acute closed flexor tendon injuries, however, usually require operative intervention for the best result. Although evaluation and diagnosis of flexor tendon injuries are relatively straightforward, diagnosis is still commonly delayed secondary to both delayed presentation and missed diagnoses. If diagnosis is delayed, operative intervention becomes less optimal and the patient may have a permanent disability regardless of treatment. Generally, athletes are able to return to their pre-injury level of participation regardless of treatment. This is a product of both the finger involved--usually ring or little--and the extent of the disability. In many instances, the athlete may even continue participation during treatment with protective splinting.

Dietary fats and immune status in athletes: clinical implications.

Athletes are competitive, train at very high levels with inadequate rest, consume too few calories, avoid fats, and may be at increased risk of infections. The immune system is sensitive to both fat intake and intense exercise, suggesting that athletes may have suppressed immune function. It has been reported that many athletes consume about 25% fewer calories than the estimated expenditure, leading to low intakes of some essential micronutrients and fats. Acute exercise has been shown to increase inflammatory and decrease antiinflammatory immune factors and may increase oxidant stress. Chronic exercise appears to improve immune competence. Lipids are powerful mediators of the immune system, and they may modulate the immunosuppressive effects of strenuous exercise. Studies have shown that a low-fat high-carbohydrate diet (15% fat, 65% CHO, 20% protein of total calories), typically eaten by athletes, increases inflammatory and decreases antiinflammatory immune factors, depresses antioxidants, and negatively affects blood lipoprotein ratios. Increasing total caloric intake by 25% to match energy expenditure and the dietary fat intake to 32% in athletes appears to reverse the negative effects on immune function and lipoprotein levels reported on a low-fat diet. Increasing the dietary fat intake of athletes to 42%, while maintaining caloric intake equal to expenditure, does not negatively affect immune competency or blood lipoproteins, whereas it improves endurance exercise performance at 60-80% of VO2max in cyclists, soldiers, and runners. There is no evidence that higher fat intakes (up to 42% of total calories), in calorically balanced diets, increase the risk of cancer, but studies are needed to determine whether the beneficial effects of higher fat diets in athletes reduce their rate of infections.

A perspective on fat intake in athletes.

Performance in endurance events is dependent upon the maximal aerobic power, the percentage of that power that can be sustained and the availability of substrates (carbohydrates [CHO] and fats). The purpose of this paper is to present a perspective of recent studies that demonstrate the role of fat intake and oxidation on endurance performance. Studies have shown that fatigue is associated with reduced muscle glycogen and that increasing muscle glycogen or blood glucose prolongs performance while increasing fat and decreasing CHO decreases performance. This has led to an emphasis on CHO intake in athletes in endurance sports, which quite often leads to low caloric intake. It is well known that trained subjects have higher levels of fat oxidative capacity, which spares glycogen during endurance sports. Data from recent studies in trained athletes, who were fed iso-caloric high-fat diets (42% to 55%) that maintained adequate CHO levels, have shown an increase in endurance in both men and women when compared to diets composed of low fat intake (10% to 15%). The magnitude of the effect on endurance was significant at high percentages of maximal aerobic power and increased as the percentage of maximal aerobic power decreased. Based on this review, a baseline diet comprising 20% protein, 30% CHO and 30% fat, with the remaining 20% of the calories distributed between CHO and fat based on the intensity and duration of the sport, is recommended for discussion and future research.

The effects of varying dietary fat on performance and metabolism in trained male and female runners.

OBJECTIVES: Low dietary fat intake has become the diet of choice for many athletes. Recent studies in animals and humans suggest that a high fat diet may increase VO2max and endurance. We studied the effects of a low, medium and high fat diet on performance and metabolism in runners. METHODS: Twelve male and 13 female runners (42 miles/week) ate diets of 16% and 31% fat for four weeks. Six males and six females increased their fat intakes to 44%. All diets were designed to be isocaloric. Endurance and VO2max were tested at the end of each diet. Plasma levels of lactate, pyruvate, glucose, glycerol, and triglycerides were measured before and after the VO2max and endurance runs. Free fatty acids were measured during the VO2max and endurance runs. RESULTS: Runners on the low fat diet ate 19% fewer calories than on the medium or high fat diets. Body weight, percent body fat (males=71 kg and 16%; females=57 kg and 19%), VO2max and anaerobic power were not affected by the level of dietary fat. Endurance time increased from the low fat to medium fat diet by 14%. No differences were seen in plasma lactate, glucose, glycerol, triglycerides and fatty acids when comparing the low versus the medium fat diet. Subjects who increased dietary fat to 44% had higher plasma pyruvate (46%) and lower lactate levels (39%) after the endurance run. CONCLUSION: These results suggest that runners on a low fat diet consume fewer calories and have reduced endurance performance than on a medium or high fat diet. A high fat diet, providing sufficient total calories, does not compromise anaerobic power.

Muscle structure with low- and high-fat diets in well-trained male runners.

Endurance capacity, maximal oxygen uptake capacity (VO2max) and quantitative muscle ultrastructural composition was analyzed in 7 well-trained male runners (mean age 37.1 years, mean VO2max 60 ml/min/kg) after a one month period of a low-fat diet (dietary fat intake 18.4% and a similar period of a high-fat diet (dietary fat intake 40.6%). Between these two interventional periods a washout period of one month was interspersed in which the nutritional fat content was approx. 32%; close to the average American Diet. During all three periods protein content of the nutrition was kept nearly constant at 15%. After the high-fat diet time to exhaustion in the endurance test increased significantly by 21% while VO2max remained unchanged. Muscle mitochondrial volume density remained unchanged while the intramyocellular fat content increased by 60%. Due to large interindividual differences in this variable this difference did not become statistically significant. While some 20% of the mitochondria are located in a subsarcolemmal location, only 10% of the lipid stores are associated with these mitochondria. Less than 2% of the mitochondrial outer surface are in contact with lipid droplets whereas 25-35% of the lipid surface is in contact with mitochondria. None of these variables is significantly altered after a high-fat diet. It is concluded that the change in endurance capacity of the subjects cannot be explained based on the structural changes observed in skeletal muscle tissue. This may be related to methodological problems associated with the determination of intramyocellular fat content.

Drug interactions affecting the efficacy of corticosteroid therapy a brief review with an illustrative case.

A drug interaction that seemed to contribute to sudden worsening of corticosteroid-stabilized vasculitis stimulated this review. A large number of drugs share with corticosteroids critical phase I metabolic steps mediated by hepatic cytochrome P450 (CYP) enzymes, particularly the individual enzyme CYP3A4. In their metabolic interaction with CYP3A4 as substrates, a growing number of these drugs have the potential to induce (upregulate) hepatic CYP3A4 levels, resulting in accelerated clearance (and reduced efficacy) of concomitantly administered glucocorticoids, which are also CYP3A4 substrates. Many other drugs can have the opposite effect, that is, they can inhibit CYP3A4 function by tight binding to its active site. This can result in reduced clearance (and augmented efficacy) of concurrently administered glucocorticoids. Current knowledge of this type of drug interaction, the drugs to watch out for, and multiple clinical reports of altered corticosteroid efficacy, are reviewed after presentation of the case illustrating potential relevance to the management of rheumatic diseases.

Closed tendon injuries of the hand and wrist in athletes.

Closed-tendon injuries of the hand and wrist are very common in the athletic population. Most of these injuries, if seen acutely, can be treated successfully with nonoperative management, although some do require operative treatment. It is those injuries, however, that go undiagnosed until the end of the season, which may result in permanent disability.

Prospective evaluation of the Ottawa Ankle Rules in a university sports medicine center. With a modification to increase specificity for identifying malleolar fractures.

In a sports medicine center, we prospectively evaluated the Ottawa Ankle Rules over 1 year for their ability to identify clinically significant ankle and midfoot fractures and to reduce the need for radiography. We also developed a modification to improve specificity for malleolar fracture identification. Patients with acute ankle injuries (< or = 10 days old) had the rules applied and then had radiographs taken. Sensitivity, specificity, and the potential reduction in the use of radiography were calculated for the Ottawa Ankle Rules in 132 patients and for the new "Buffalo" rule in 78 of these patients. There were 11 clinically significant fractures (fracture rate, 8.3% per year). In these 132 patients, the Ottawa Ankle Rules would have reduced the need for radiography by 34%, without any fractures being missed (sensitivity 100%, specificity 37%). In 78 patients, the specificity for malleolar fracture for the new rule was significantly greater than that of the Ottawa Ankle Rules malleolar rule (59% versus 42%), sensitivity remained 100%, and the potential reduction in the need for radiography (54%) was significantly greater. The Ottawa Ankle Rules could significantly reduce the need for radiography in patients with acute ankle and midfoot injuries in this setting without missing clinically significant fractures. The Buffalo modification could improve specificity for malleolar fractures without sacrificing sensitivity and could significantly reduce the need for radiography.

Effect of a high or a low fat diet on cardiovascular risk factors in male and female runners.

Dietary fat may be associated with coronary heart disease (CHD). Studies suggest that restricting fat intake may compromise endurance performance and that increasing fat intake may improve endurance performance. We studied the effects of varying dietary fat intake on CHD risk factors in runners. Twelve male and 13 female runners increased fat from 16% to 30% of daily calories (4 wk each). Of this group, six males and six females increased fat to 42% of daily calories (4 wk). Physiological and lipoprotein risk factors were measured after each diet. Results were analyzed by repeated measures ANOVA. Increasing dietary fat from 16% to 42% of daily calories did not change adiposity, weight, heart rate, blood pressure, serum triglycerides, total cholesterol, LDL cholesterol. Apolipoprotein B, or the Apo A1/Apo B ratio. Compared with those eating higher fat, subjects eating 16% fat had lower HDL cholesterol (50 +/- 3 vs 62 +/- 3 mg.dl-1, P < 0.0001) and Apolipoprotein A1 (111 +/- 6 v. 134 +/- 6 mg/dl, P < 0.0005) and a higher TC/HDL-C ratio (4.05 +/- 0.27 vs 3.42 +/- 0.24, P < 0.0005). Runners who increased fat intake to 42% further raised HDL cholesterol (64 +/- 6 to 69 +/- 5 mg.dl-1, P < 0.04) without adversely affecting other lipoproteins. In conclusion, a 42% fat diet maintained favorable CHD risk factors in female and male runners whereas a 16% fat diet lowered Apo A1 and HDL-C and raised the TC/HDL-C ratio.

The association of cardiac dystrophin with myofibrils/Z-disc regions in cardiac muscle suggests a novel role in the contractile apparatus.

Dystrophin serves a variety of roles at the cell membrane through its associations, and defects in the dystrophin gene can give rise to muscular dystrophy and genetic cardiomyopathy. We investigated localization of cardiac dystrophin to determine potential intracellular sites of association. Subcellular fractionation revealed that while the majority of dystrophin was associated with the sarcolemma, about 35% of the 427-kDa form of dystrophin was present in the myofibrils. The dystrophin homolog utrophin was detectable only in the sarcolemmal membrane and was absent from the myofibrils as were other sarcolemmal glycoproteins such as adhalin and the sodium-calcium exchanger. Extraction of myofibrils with KC1 and detergents could not solubilize dystrophin. Dystrophin could only be dissociated from the myofibrillar protein complex in 5 M urea followed by sucrose density gradient centrifugation where it co-fractionated with one of two distinctly sedimenting peaks of actin. Immunoelectron microscopy of intracellular regions of cardiac muscle revealed a selective labeling of Z-discs by hystrophin antibodies. In the genetically determined cardiomyopathic hamster, strain CHF 147, the time course of development of cardiac insufficiency correlated with an overall 75% loss of myofibrillar dystrophin. These findings collectively show that a significant pool of the 427-kDa form of cardiac dystrophin was specifically associated with the contractile apparatus at the Z-discs, and its loss correlated with progression to cardiac insufficiency in genetic cardiomyopathy. The loss of distinct cellular pools of dystrophin may contribute to the tissue-specific pathophysiology in muscular dystrophy.

Pitfalls of endoscopic carpal tunnel release.

The article details various pitfalls of endoscopic carpal tunnel release. Highlighted are the two-portal Chow technique and the single-portal Agee technique.

Allergic reactions to cyclophosphamide: delayed clinical expression associated with positive immediate skin tests to drug metabolites in five patients.

BACKGROUND: Cyclophosphamide (CP) is one of the relatively few drugs implicated in systemic allergic reactions for which the metabolites are well known. Formation of CP metabolites is a multistep, time-dependent process (hours) with significant interindividual differences. Although allergic reactions to CP have been recorded in 17 previous reports, skin testing with CP or its metabolites has been included in only five. We now describe five patients receiving monthly cycles of intravenous CP whose allergic reactions included clinical features of type I hypersensitivity but were atypical in their markedly delayed onset (i.e., 8 to 16 hours in patients 1 to 4 and 10 days in patient 5). OBJECTIVE: The objective was to investigate these late-developing clinical reactions by skin testing with CP and two of its major metabolites. METHODS: The five patients and a control group receiving intravenous CP uneventfully were studied by the same skin test protocol. RESULTS: The four individuals in the control group were unreactive to CP or its metabolites. All five patients with late-onset allergic reactions had positive immediate skin test results to CP metabolites but not to CP itself. We propose that the allergic reactions in patients 1 to 4 were mediated, wholly or in major part, by IgE antibodies reactive with allergens derived from time-dependent drug metabolites. The 10-day lag time in patient 5 is unexplained. Immunomodulation by the underlying malignancies or by the immunosuppressive drugs could have contributed. CONCLUSION: IgE-mediated allergic drug reactions may have a delayed onset if the allergen is a time-dependent drug metabolite, illustrated in this study by CP.

The role of dietary fat on performance, metabolism, and health.

This paper presents a model to evaluate the nutritional status of trained athletes based on work in our laboratory as well as others. The model proposes that substrate use is set by the muscle fibers recruited, based on the exercise intensity. Second, the substrate available is primarily determined by the intramuscular stores. In trained athletes, intramuscular fat plays an important role in metabolism at exercise intensities as high as 80% of maximal aerobic power. Based on these factors, increasing the fat in the diet (while maintaining adequate intramuscular glycogen) increases VO2max and intramuscular stores of fat (presumably due to increased mitochondrial volume). These two factors result in a significant increase in the time to exhaustion at set levels of exercise (endurance). It also appears that fatigue is associated with depletion of either glycogen or fat. These conclusions hold true for athletes on diets where sufficient calories are taken in to meet demands and for exercise levels below 80% of VO2max, where primarily slow-twitch oxidative fibers are used. These data may not apply in exercise where predominantly fast-twitch fibers are used. Also, these data do not apply to runners eating a hypocaloric diet, where reducing the percentage of carbohydrates may compromise their glycogen stores. It would appear that the fat in the diet can be increased to a very high level without compromising the cardiovascular or immune systems of athletes. Moreover, it can be proposed that these data could be applied to sedentary persons, as long as they are isocaloric. This would imply that the fat consumed in the diet would be used in the muscle, as in the runners, although at a lower level. Thus, the dietary intake should be matched in both total calories and percentage of fats and carbohydrates to calories consumed by daily activity. It should be cautioned that if glycogen and fat stores are compromised, protein resynthesis is inhibited and loss of muscle mass may result. This has a negative effect on the athlete's ability to perform at high levels.

Density and solubility of nafion: recast, annealed, and commercial films.

The density of Nafion membranes wetted in water and acetonitrile and the solubility of Nafion in a 50:50 ethanol/water mixture are reported. Commercially available membranes, solution recast membranes, and recast membranes thermally processed for varying lengths of time were examined. Unheated recast membranes were found to be ∼20% less dense in water than both commercial membranes and recast membranes heated at 140 °C for 40, 50, and 60 min. For heating times of ≥40 min, the density of recast membranes in water was invariant and equal to the density of commercial films. Similarly, in acetonitrile, commercial membranes and films heated for 1 h had the same density; unheated recast films were ∼25% less dense. Nafion density in acetonitrile was ∼15% less than that in water. Acid pretreatment reduced Nafion film density by ∼15%. Unheated recast films were 22-100% soluble in a sonicated ethanol/water mixture. Commercial membranes and recast films heated for as little as 10 min were insoluble under the same conditions.